Modified polyurethane liquid polymer compositions

ABSTRACT

A novel, heat curable, liquid polymer composition is disclosed which comprises a modified polyurethane oligomer containing terminal ethylenic unsaturation and a free radical generating catalyst. In a preferred embodiment, the polymer composition further includes at least one additional component selected from a reinforcing agent and a filler.

This is a division of application Ser. No. 364,575, filed Apr. 1, 1982,which is, in turn, a continuation-in-part of application Ser. No.203,213, filed Nov. 3, 1980, now abandoned.

This invention relates to a select liquid polymer composition containinga modified polyurethane oligomer having terminal ethylenic unsaturation.

In recent years, there has been a steady increase in the use ofreinforced plastic materials for exterior components in automotiveconstruction. Further increases in the utilization of plastics can beexpected as automobile manufacturers continue to strive to meet vehicleweight reduction goals.

In the area of rigid plastic automotive components,fiberglass-reinforced thermosetting polyester resins have beenextensively employed. This can be attributed to their overall physicalcapabilities (e.g., dimensional stability, strength, high temperatureresistance, and paint adhesion). Other advantages include facility ofhandling and machining. However, these polyester systems still presentcertain deficiencies such as a brittle nature, which can lead to severeimpact and fatigue problems. There is also a need to improve surfacecharacteristics and shrinkage control.

To overcome these problems, various additives have been introduced intopolyester sheet molding compounds (SMC) and bulk molding compounds(BMC). For example, in U.S. Pat. No. 4,020,036 issued to Aubrey South,Jr. on Apr. 26, 1977, liquid polymers, such as polybutadiene, are addedin order to toughen polyester products. However, since these materialsare not inherently compatible with polyester, these additives cannot beadded to the polyester, until it is time to mix the resin with thefiberglass. Saturated diacids or long-chain glycols also have been usedin preparing polyester resins; the resulting products have beenflexibilized, but, at the cost of lower mechanical and thermalproperties.

Another approach involves the introduction of polyurethane systems intopolyester resins. In U.S. Pat. No. 4,062,826 issued to Francis GowlandHutchinson et al. on Dec. 13, 1977, precursors of a cross-linkedpolyurethane are polymerized within a mixture of ethylenicallyunsaturated polyester and vinyl monomer to form a product with aninterpenetrating polyurethane gel network within the polyestercross-linked structure. While higher impact properties are reported tobe achieved, the fine surface finish required for automotive body partapplications is not accomplished. See Forger, G., Toughened SMC,Plastics World, page 63 (June 1978).

Now it has been discovered, according to the present invention, that aheat curable liquid polymer composition can be prepared comprising amodified polyurethane oligomer containing terminal ethylenicunsaturation and a free radical generating catalyst. Such a compositionfeatures the advantages of a one-component storage stable system thatrequires only heat for activation; the cured composition is useful inpreparing a wide variety of coatings and castings. In a preferred formof the invention, the polymer composition may include at least oneadditional component selected from a reinforcing agent and a filler. Thecured plastic products feature improved impact properties and aresuitable for many of the same utilities as thermoset polyester resincompositions such as parts for automotive body applications.

The polyurethane oligomer that is utilized according to the invention isprepared by first reacting an organic polyisocyanate with an isocyanatereactive group-containing unsaturated monomer using standard proceduresand in such proportions as to yield an isocyanate-terminated prepolymerof controlled molecular weight having a free NCO content ranging fromabout 0.5% to about 30%. Preferably, the prepolymer has a free NCOcontent ranging from about 10% to about 20%.

Any suitable organic polyisocyanate, or mixture of polyisocyanates, maybe employed in preparing the polyurethane oligomer. Illustrative aretoluene diisocyanate, such as the 80:20 and the 65:35 mixtures of the2,4- and 2,6-isomers, ethylene diisocyanate, propylene diisocyanate,methylene-bis (4-phenyl)isocyanate, methylene-bis (4-cyclohexyl)isocyanate, xylene diisocyanate, 3,3'-bitoluene-4,4'-diisocyanate,hexamethylene diisocyanate, naphthalene-1,5-diisocyanate, isophoronediisocyanate, the polymeric isocyanates such as polyphenylenepolymethylene isocyanate, and the like, and mixtures thereof. Inaccordance with a particularly preferred embodiment of the invention,there is employed an isomeric mixture of 2,4- and 2,6-toluenediisocyanate in which the weight ratio of the 2,4-isomer to the2,6-isomer is from about 60:40 to about 90:10, and more preferably fromabout 65:35 to about 80:20.

Suitable isocyanate reactive group-containing unsaturated monomersinclude hydroxyl group-containing or amino group-containing acrylates,substituted acrylates such as methacrylates, acrylamides, andsubstituted acrylamides, such as methacrylamides, and mixtures thereof.Illustrative isocyanate reactive group-containing unsaturated monomersare hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethylmethacrylate, hydroxyethyl acrylamide, hydroxypropyl acrylamide,hydroxyethyl methacrylamide, and the like. Acrylates and methacrylatesare preferred, with hydroxyethyl acrylate, hydroxypropyl acrylate andhydroxyethyl methacrylate being the most preferred.

To form the polyurethane oligomer that is utilized according to theinvention, the prepared isocyanate-terminated prepolymer, as definedabove, is then reacted with a polyol. The reaction is carried out usingmethods well known in the art and employing such relative proportions ofthe reactants so as to achieve an oligomer product having an equivalentratio of NCO to active hydrogen from about 0.5/1 to about 2/1,preferably from about 0.7/1 to about 1.5/1, and most preferably fromabout 0.8/1 to about 1.2/1. By reaction of the isocyanate-terminatedprepolymer with the polyol, a controlled molecular weight polyurethaneoligomer with terminal reactive unsaturation is produced.

Preferably, the reaction is accelerated by employing a catalyst; commonurethane catalysts, e.g., tertiary amines and metal compounds such asstannous octoate or dibutyltin dilaurate may be used. Any catalyticamount may be employed; illustratively, such amount varies, depending onthe particular catalyst utilized, from about 0.01% to about 1% by weightof the polyurethane oligomer. It is also preferred to carry out thereaction in the presence of a reactive copolymerizable solvent. Suitablecopolymerizable solvents include vinylidene compounds such as styrene,vinyl toluene, methacrylic esters, acrylic esters, divinyl benzene, andthe like, familiar to those skilled in the art. The amount ofcopolymerizable solvent employed may be varied over a wide range.Generally, however, the copolymerizable solvent is employed in an amountof from about 0 to about 100 parts by weight per 100 parts by weight ofthe polyurethane oligomer of the present invention.

The polyol reactant used in the polyurethane oligomer formationcomprises a select combination of polyols, i.e., a high functionalitypolyol and a chain extender. More in detail, the high functionalitypolyol is selected from polyether polyols and mixtures of two or moresuch compounds. The high functionality polyol, or mixture of highfunctionality polyols, should have an average equivalent weight rangingfrom about 75 to about 500. Preferably, the average equivalent weight isabout 100 to about 200. The average functionality of the highfunctionality polyol or high functionality polyol blend is at leastabout 3, and preferably about 3.3 to about 6.

Suitable high functionality polyether polyols include variouspolyoxyalkylene polyols and mixtures thereof. These can be prepared,according to well-known methods, by condensing an alkylene oxide, or amixture of alkylene oxides using random or step-wise addition, with apolyhydric initiator or a mixture of polyhydric initiators. Illustrativealkylene oxides include ethylene oxide, propylene oxide, butylene oxide,amylene oxide, aralkylene oxides such as styrene oxide, and thehalogenated alkylene oxides such as trichlorobutylene oxide and soforth. The most preferred alkylene oxide is propylene oxide or a mixturethereof with ethylene oxide using random or step-wise oxyalkylation.

The polyhydric initiator used in preparing the high functionalitypolyether polyol reactant comprises a carbohydrate or a carbohydratederivative. Illustrative are sucrose, dextrose, methyl glucoside,mixtures thereof, and mixtures of sucrose or dextrose or methylglucoside with at least one aliphatic diol or triol. Exemplificative ofthe latter are water, ethylene glycol, propylene glycol, the butyleneglycols, glycerol, trimethylolpropane, triethylolpropane, thealkanolamines, and the like, and mixtures thereof.

A preferred group of polyhydric initiators for use in preparing the highfunctionality polyether polyol reactant is one which comprises mixturesof sucrose or dextrose or methyl glucoside with an aliphatic triol,preferably glycerol.

The alkylene oxide-polyhydric initiator condensation reaction ispreferably carried out in the presence of a catalyst such as KOH as iswell known in the art. In effecting the reaction, a sufficientproportion of alkylene oxide is used as to provide a final polyolproduct having an average equivalent weight of about 75 to about 500,preferably about 100 to about 200. The catalyst is thereafter preferablyremoved, leaving a high functionality polyether polyol which is readyfor use in preparing the polyurethane oligomer of the invention.

As indicated above, in forming the polyurethane oligomer, a chainextender is included in the polyol reactant. These chain extenders havean average equivalent weight ranging from about 31 to about 4,000,preferably from about 31 to about 500, and an average functionality ofabout 2. Suitable chain extenders include: (a) low molecular weightdiols, such as ethylene glycol, butane diol, pentane diol, hexane diol,2-ethyl-1,3-hexane diol, dipropylene glycol, diethylene glycol,triethylene glycol, bisphenol A, and the like, and mixtures thereof; and(b) polyether diols, such as propylene oxide diols, propyleneoxide-ethylene oxide diols, etc., and mixtures thereof. Dipropyleneglycol, tripropylene glycol and 2-ethyl-1,3-hexane diol are particularlypreferred. Usually a proportion of chain extender is employed whichranges from about 20 to about 1,500, and preferably from about 50 toabout 900, parts by weight per every 100 parts by weight of the highfunctionality polyol.

The modified polyurethane oligomer liquid polymer system is polymerizedand cured in the presence of a heat activated free radical generatingcatalyst. The actual curing conditions may vary over wide ranges and aregenerally dependent on the nature and amount of the particular catalystemployed. Suitable free radical generating catalysts include peroxide orazo type compounds, known to those in the art. Typical peroxidecatalysts are illustrated by organo peroxides and hydroperoxides such asbenzoyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, laurylperoxide, cyclohexanone peroxide, t-butyl perbenzoate, t-butylhydroperoxide, t-butylbenzene hydroperoxide, cumene hydroperoxide,t-butyl peroctoate, and the like. Typical azo compounds areazobis-isobutyronitrile, 2-t-butylazo-2-cyano-4-methylpentane, and4-t-butylazo-4-cyanovaleric acid. The preferred catalysts are peroxidecatalysts. In particular, preferred peroxide catalysts are t-butylperoctoate, t-butyl perbenzoate, and mixtures thereof. Any suitablecatalytic amount may be employed; however, the catalyst generally isused in an amount from about 0.1 to about 10 parts by weight per 100parts by weight of the polyurethane oligomer.

The composition of the present invention also may include other standardingredients, if desired, such as internal mold release agents, e.g.,calcium, zinc, magnesium, or sodium stearate. Low shrink or impactadditives also may be included, if desired. Pigments, dyes, stabilizers,thixotropes, and various other additives familiar to those skilled inthermosetting polyester technology also may be added.

In one preferred embodiment of the invention, the composition alsocontains at least one of a filler or a reinforcement material, andpreferably both. Any material known to those in the art as beingsuitable as a filler may be employed. Generally, a variety of materials,e.g., finely divided solids including CaCO₃, clay, alumina, talc, glassmicrospheres, and the like, may be utilized. Also, any suitablereinforcement material may be used, such as chopped fiberglass, carbonfibers, asbestos fibers, boron nitride whiskers, and the like. Theamount of filler generally included in the formulation may varyconsiderably, but usually ranges from about 20 to about 400, andpreferably from about 100 to about 220, parts by weight per 100 parts byweight of the polyurethane oligomer. The amount of reinforcing agentadded to the formulation may also vary over a wide range; however, atypical formulation will generally contain from about 10 to about 150,and preferably from about 60 to about 130, parts by weight per 100 partsby weight of the polyurethane oligomer.

The following examples are provided to further illustrate the invention.All parts are by weight unless otherwise specified.

PREPARATION OF POLYURETHANE OLIGOMER Example 1

To 87.0 grams (1.0 eq.) of diisocyanate, 141.8 grams of styrene and 0.71grams of hydroquinone were added dropwise with stirring 65.0 grams (0.5eq.) of unsaturated monomer over a period of 30 minutes. The reactiontemperature rose from 25° to 30° C., and the mixture was stirred withoutheating for 60 minutes. To this mixture was added dropwise with stirringa mixture of 36.7 grams (0.25 eq.) of a high functionality polyetherpolyol and 24.0 grams (0.25 eq.) of a chain extender over a period of 45minutes. The resulting mixture was stirred for 45 minutes withoutheating, when 0.68 ml of dibutyltin dilaurate was added. The reactiontemperature climbed from 33° to 65° C. within 5 minutes. The mixture wasthen heated to 70° C. and was stirred at 70° C. for 3 hours. The producthad a viscosity of 1,130 cps at 26° C.

The polyether polyol used had a molecular weight of about 650 and wasprepared by condensing a sucrose/glycerol mixture with propylene oxideto a final hydroxyl number of about 375. The diisocyanate was a mixtureof toluene diisocyanate isomers (80:20 mixture of 2,4/2,6-isomers). Thechain extender was tripropylene glycol. The unsaturated monomer washydroxypropyl acrylate.

Examples 2-24

Additional polyurethane oligomers were prepared employing the sameconditions as outlined in Example 1. Different reactants and proportionsof reactants were used, however, to form prepolymers. These prepolymerswere reacted with suitable proportion of polyol reactant to produceoligomers according to the invention. Table I outlines the oligomercompositions prepared according to Examples 2-24.

                                      TABLE I                                     __________________________________________________________________________    OLIGOMER COMPOSITIONS                                                                                  Polyol Reactant                                                               High                                                                  Unsaturated                                                                           Functionality                                                         Monomer (eq.)                                                                         Polyol (eq.)                                                                          Chain Extender (eq.)                         Example                                                                            Diisocyanate.sup.○1 (eq.)                                                          A.sup.○2                                                                   B.sup.○3                                                                   C.sup.○4                                                                   D.sup.○5                                                                   E.sup.○6                                                                   F.sup.○7                                                                   G.sup.○8                                                                   H.sup.○9                  __________________________________________________________________________     1   1.0         --  0.5 0.25                                                                              --  --  --  0.25                                                                              --                                2.sup.○10                                                                  1.0         0.5 --  0.25                                                                              --  --  --  0.25                                                                              --                                3   2.0         1.0 --  0.75                                                                              --  0.25                                                                              --  --  --                                4   2.0         1.0 --  0.5 --  0.5 --  --  --                                5   2.0         1.0 --  --  0.5 0.5 --  --  --                                6   2.0         --  1.0 --  0.5 0.5 --  --  --                                7   2.0         --  1.0 0.5 --  0.5 --  --  --                                8   2.0         --  1.0 --  0.5 0.5 --  --  --                                9   2.0         --  1.0 --  0.5 --  0.5 --  --                               10   2.0         --  1.0 0.75                                                                              --  0.25                                                                              --  --  --                               11   2.0         --  1.0 --  0.75                                                                              0.25                                                                              --  --  --                               12   2.0         1.0 --  --  0.5 --  0.5 --  --                               13   2.0         1.0 --  0.5 --  --  0.5 --  --                               14   2.0         1.0 --  0.75                                                                              --  --  --  --  0.25                             15   2.0         1.0 --  --  0.75                                                                              --  --  --  0.25                             16   2.0         1.0 --  --  0.75                                                                              0.25                                                                              --  --  --                               17   2.0         --  1.0 0.50                                                                              --  --  0.5 --  --                               18   2.0         --  1.0 0.50                                                                              --  --  --  0.5 --                               19   2.0         --  1.0 --  0.75                                                                              --  --  0.25                                                                              --                               20   2.0         --  1.0 0.75                                                                              --  --  --  0.25                                                                              --                               21   2.0         --  1.0 --  0.50                                                                              --  --  0.5 --                               22   2.0         1.0 --  --  0.50                                                                              --  --  0.5 --                               23   2.0         1.0 --  0.5 --  --  --  0.5 --                               24   2.0         1.0 --  0.75                                                                              --  --  --  0.25                                                                              --                               __________________________________________________________________________     .sup.○1 The diisocyanate is a mixture of toluene diisocyanate          isomers (80:20 mixture of 2,4/2,6isomers).                                    .sup.○2 Hydroxyethyl acrylate.                                         .sup.○3 Hydroxypropyl acrylate.                                        .sup.○4 A polyether polyol having a molecular weight of about 650      and an average functionality of about 4.25 and prepared by condensing a       sucrose/glycerol mixture with propylene oxide to a final hydroxyl number      of about 375.                                                                 .sup.○5 A polyether polyol having a molecular weight of about 480      and an average functionality of about 4.54 and prepared by condensing a       sucrose/glycerol mixture with propylene oxide to a final hydroxyl number      of about 530.                                                                 .sup.○6 2-Ethyl-1,3-hexane diol.                                       .sup. ○7 Dipropylene glycol.                                           .sup.○8 Tripropylene glycol.                                           .sup.○9 A polyether polyol having a molecular weight of about 650      and prepared by endcapping a propoxylated dipropylene glycol precursor        with ethylene oxide to a final hydroxyl number of about 173.                  .sup.○10 Instead of 141.8, 137.1 grams of styrene were used.      

Example 25

To 174 grams (2.0 eq.) of diisocyanate and 271.5 grams of styrene wereadded dropwise with stirring 132 grams (1.0 eq.) of unsaturated monomerover a period of 1 hour. The mixture was stirred without heating for 1hour. To this mixture was added dropwise with stirring a mixture of 55.6grams (0.625 eq.) of a high functionality polyether polyol and 45.6grams (0.625 eq.) of a chain extender over a period of 1 hour. Theresulting mixture was stirred for 1 hour without heating, when 0.2 ml ofdibutyltin dilaurate was added. The mixture was then heated to 70° C.and was stirred at 70° C. for 3 hours.

The polyether polyol used had a molecular weight of about 480 and wasprepared by condensing a sucrose/glycerol mixture with propylene oxideto a final hydroxyl number of about 530. The diisocyanate was a mixtureof toluene diisocyanate isomers (80:20 mixture of 2,4/2,6-isomers). Thechain extender was 2-ethyl-1,3-hexane diol. The unsaturated monomer washydroxypropyl acrylate.

Example 26

A. To 348 grams (4.0 eq.) of diisocyanate were added dropwise withstirring 232 grams (2.0 eq.) of unsaturated monomer over a period of 105minutes. The reaction temperature was maintained below 50° C. during theaddition period by external cooling with a cooled water bath. Themixture was stirred for one additional hour below 35° C. At the end ofthis period, 387 grams of styrene were added to the mixture. No freeunsaturated monomer was detected in the sample after standing overnight.

B. To a mixture of 26.3 grams (0.25 eq.) of a high functionalitypolyether polyol and 18.3 grams (0.25 eq.) of a chain extender in 29.7grams of styrene were added 242 grams (0.50 eq.) of the intermediatefrom part A dropwise over a period of 30 minutes. After stirring for 1hour at room temperature, 0.5 ml of stannous octoate was added. Thereaction temperature climbed to 50° C. after 20 minutes. The mixture wasstirred for an additional 40 minutes after the peak exotherm wasreached, at which point 50 mg of hydroquinone were added and the mixturewas heated to 75° C. The mixture was stirred at 75° C. for 2 hours. Atthe end of the heating period, no isocyanate peak was observed in aninfrared spectrum. The product had a viscosity of 2,960 cps at 22° C.

The diisocyanate was a mixture of toluene diisocyanate isomers (80:20mixture of 2,4/2,6-isomers). The unsaturated monomer was hydroxyethylacrylate. The polyether polyol used had a molecular weight of about 480and was prepared by condensing a sucrose/glycerol mixture with propyleneoxide to a final hydroxyl number of about 530. The chain extender was2-ethyl-1,3-hexane diol.

PREPARATION OF POLYURETHANE MOLDINGS Examples 27-41

Test panels were prepared containing polyurethane oligomers preparedaccording to Examples 3-13 and 16-19. The molding formulation used islisted in Table II below. The following procedure was followed in thepreparation of the cured composites.

a. Into a high shear mixing device were added the polyurethane oligomer,styrene, catalyst, and mold release agent.

b. The filler was added gradually and mixed until a homogeneous pastewas obtained.

c. Next chopped fiberglass was gradually added to the paste in atwo-roll mill and the mix was worked the minimal length of time toachieve good wet out of the glass without significant breakdown.

d. The uncured mix was then placed in a mold between the platens of acompression molding machine and cured under pressure (2,000 psi) for 3minutes at 300°-325° F.

e. Alternatively to (d), the mixture may be added by a hopper device tothe screw system of an injection molding device to produce an injectionmolded part, or the mix may be made up on an SMC machine for latercompression or injection molding.

The physical properties of panels prepared in this manner are includedin Table III below. The physical properties were determined inaccordance with standard test procedures: Flexural modulus and flexuralstrength--ASTM D790; tensile strength--ASTM D3574; izod--ASTM D256; andcoefficient of thermal expansion--ASTM D696.

                  TABLE II                                                        ______________________________________                                        POLYURETHANE MOLDING                                                          FORMULATION (SMC/BMC)                                                         Component          Parts by Weight                                            ______________________________________                                        Polyurethane Oligomer                                                                            100     (40% Styrene)                                      Tertiary Butyl Perbenzoate                                                                       0.5                                                        Tertiary Butyl Peroctoate.sup.○1                                                          0.5                                                        Zinc Stearate      3.0                                                        Calcium Carbonate  185                                                        1/2 Inch Glass     75                                                         ______________________________________                                         .sup.○1 Commerically available from Lupersol Co. under the             designation "PDO",  understood to consist of 50% tertiary butyl peroctoat     and 50% dioctyl phthalate.                                               

                                      TABLE III                                   __________________________________________________________________________    PHYSICAL PROPERTIES OF POLYURETHANE OLIGOMER COMPOSITES                                   Tensile                                                                            Flexural                                                                           Flexural                                                Polyurethane                                                                              Strength                                                                           Strength                                                                           Modulus ×                                                                     Izod (ft.-lb./in.)                                                                       Surface.sup.○1                                                               Gloss.sup.○2              Example                                                                            Oligomer                                                                             (psi)                                                                              (psi)                                                                              10.sup.6 (psi)                                                                      Notched                                                                            Unnotched                                                                           (1-10)                                                                              (%)                              __________________________________________________________________________    27   Example  3                                                                           6240 10,100                                                                             0.870 12.5 13.6  5.5   70                               28   Example  4                                                                           6320 14,400                                                                             1.04  16.1 17.4  5.0   60                               29   Example 18                                                                           3140 12,000                                                                             1.30  9.1  16.1  6.0   65                               30   Example  5                                                                           4310 12,800                                                                             0.900 8.4  17.0  4.5   60                               31   Example 13                                                                           2910  9,700                                                                             1.30  11.0 10.0  7.5   75                               32   Example 12                                                                           3690 13,200                                                                             1.46  12.6 12.2  6.5   70                               33   Example 16                                                                           4900 16,200                                                                             1.23  9.5  9.3   5.0   50                               34   Example 17                                                                           3930 15,600                                                                             1.52  11.7 12.7  5.5   65                               35   Example 10                                                                           3930 11,200                                                                             1.48  8.2  13.6  7.0   70                               36   Example  7                                                                           6140 12,800                                                                             1.20  9.6  10.6  5.0   50                               37   Example 11                                                                           4400 10,500                                                                             1.15  10.2 11.3  7.5   85                               38   Example  6                                                                           6160 11,000                                                                             0.98  9.0  12.0  5.0   75                               39   Example 19                                                                           5200 15,200                                                                             1.34  9.7  12.8  5.5   60                               40   Example  9                                                                           3810 13,400                                                                             1.35  11.0 13.4  5.5   60                               41   Example  8                                                                           5680 13,600                                                                             1.19  12.4 10.4  7.0   85                               __________________________________________________________________________     .sup.○1 The surface is rated subjectively from 1-10, 10 having the     smoothness of glass while 1 is fairly rough and uneven surface.               .sup.○2 Gloss is a subjective value.                              

PREPARATION OF POLYURETHANE MOLDINGS Examples 42-52

Test panels were prepared containing polyurethane oligomers preparedaccording to Examples 3, 4, 6, 10-13 and 16-19. The following procedurewas followed in the preparation of the cured panels.

a. The polyurethane oligomer was mixed with a free radical generatingcatalyst.sup. 1 , and the resulting mixture was degassed by placement ina vacuum dessicator at about 1-10 torr pressure for a period ofapproximately 1-2 minutes or until initial foaming subsided.

b. The degassed mixture was poured into a mold formed by glass platescoated with a liquid mold release agent, such as "MR515" commerciallyavailable from Greenchem Products, Inc., and held apart by one-sixteenthinch spacers.

c. The mold was then placed in an oven at 120° C. for 1 hour.

The physical properties of panels prepared in this manner are includedin Table IV below. The physical properties were determined in accordancewith standard test procedures: Flexural modulus and flexural strength--ASTM D790; tensile strength --ASTM D3574; izod --ASTM D256; andcoefficient of thermal expansion --ASTM D696.

                                      TABLE IV                                    __________________________________________________________________________    PHYSICAL PROPERTIES OF CURED POLYURETHANE OLIGOMERS                                       Tensile                                                                            Flexural                                                                           Flexural                                                Polyurethane                                                                              Strength                                                                           Strength                                                                           Modulus ×                                                                     Izod (ft.-lb./in.)                                Example                                                                            Oligomer                                                                             (psi)                                                                              (psi)                                                                              10.sup.6 (psi)                                                                      Notched                                                                            Unnotched                                    __________________________________________________________________________    42   Example  3                                                                           5690 12,700                                                                             0.526 1.59 4.00                                         43   Example  4                                                                           5380 17,000                                                                             0.541 1.69 3.20                                         44   Example  6                                                                           5840 13,000                                                                             0.540 1.86 4.00                                         45   Example 10                                                                           6280 16,400                                                                             0.495 1.73 4.50                                         46   Example 11                                                                           6310 18,600                                                                             0.567 1.54 4.37                                         47   Example 12                                                                           4670 13,600                                                                             0.535 1.80 3.75                                         48   Example 13                                                                           5060 16,200                                                                             0.525 2.00 4.00                                         49   Example 16                                                                           9910 13,200                                                                             0.414 1.87 4.95                                         50   Example 17                                                                           8500 14,700                                                                             0.461 1.71 4.47                                         51   Example 18                                                                           6880 17,300                                                                             0.529 1.60 4.43                                         52   Example 19                                                                           7600 18,300                                                                             0.546 1.84 4.22                                         __________________________________________________________________________

What is claimed is:
 1. A process for preparing a polyurethane polymerproduct comprising mixing a polyurethane oligomer and a heat activatedfree radical generating catalyst, and then heating said mixture at atemperature adequate to activate said catalyst and cure said mixture,said polyurethane oligomer having an equivalent ratio of NCO to activehydrogen from about 0.5/1 to about 2/1 and being prepared by reacting(a)an isocyanate-terminated prepolymer having a final free NCO contentranging from about 0.5% to about 30% which is the product of reacting(1)an organic polyisocyanate with (2) an isocyanate reactivegroup-containing unsaturated monomer selected from the group consistingof(i) hydroxyalkyl acrylates, (ii) hydroxyalkyl methacrylates, (iii)hydroxyalkyl acrylamides, (iv) hydroxyalkyl methacrylamides, (v)aminoalkyl acrylates, (vi) aminoalkyl methacrylates, (vii) aminoalkylacrylamides, (viii) aminoalkyl methacrylamides, and (ix) mixturesthereof, wherein alkyl is ethyl or propyl, with (b) a polyol reactantcomprising(1) a high functionality polyol having an average equivalentweight of from about 75 to about 500 and an average functionality of atleast about 3, said high functionality polyol being prepared by reactingan alkylene oxide, or a mixture of alkylene oxides, with a polyhydricinitiator comprising a carbohydrate or a carbohydrate derivative, and(2) a chain extender having an average equivalent weight from about 31to about 4,000 and an average functionality of about 2, said chainextender being employed in an amount ranging from about 20 to about1,500 parts by weight per 100 parts by weight of said high functionalitypolyol.
 2. The process of claim 1, wherein:said high functionalitypolyol has an average equivalent weight of about 100 to about 200, saidisocyanate-terminated prepolymer has a final free NCO content rangingfrom about 10% to about 20%, and said polyurethane oligomer has anequivalent ratio of NCO to active hydrogen from about 0.8/1 to about1.2/1.
 3. A polyurethane polymer product prepared by mixing apolyurethane oligomer and a heat activated free radical generatingcatalyst, and then heating said mixture at a temperature adequate toactivate said catalyst and cure said mixture, said polyurethane oligomerhaving an equivalent ratio of NCO to active hydrogen from about 0.5/1 toabout 2/1 and being prepared by reacting(a) an isocyanate-terminatedprepolymer having a final free NCO content ranging from about 0.5% toabout 30% which is the product of reacting(1) an organic polyisocyanatewith (2) an isocyanate reactive group-containing unsaturated monomerselected from the group consisting of(i) hydroxypropyl methacrylate,(ii) hydroxypropyl methacrylamide, (iii) aminoalkyl acrylates, (iv)aminoalkyl methacrylates, (v) aminoalkyl acrylamides, (vi) aminoalkylmethacrylamides, and (vii) mixtures thereof, wherein alkyl is ethyl orpropyl, with (b) a polyol reactant comprising(1) a high functionalitypolyol having an average equivalent weight of from about 75 to about 500and an average functionality of at least about 3, said highfunctionality polyol being prepared by reacting an alkylene oxide, or amixture of alkylene oxides, with a polyhydric initiator comprising acarbohydrate or a carbohydrate derivative, and (2) a chain extenderhaving an average equivalent weight from about 31 to about 4,000 and anaverage functionality of about 2, said chain extender being employed inan amount ranging from about 20 to about 1,500 parts by weight per 100parts by weight of said high functionality polyol.
 4. The polyurethanepolymer product of claim 3, wherein:said high functionality polyol hasan average equivalent weight of about 100 to about 200, saidisocyanate-terminated prepolymer has a final free NCO content rangingfrom about 10% to about 20%, and said polyurethane oligomer has anequivalent ratio of NCO to active hydrogen from about 0.8/1 to about1.2/1.